The invention relates to a service brake device for vehicles, comprising at least one compressed-air actuated service brake cylinder with at least one piston and/or a diaphragm, which on the one hand delimits a pressure chamber, which for applying the service brake can be supplied with compressed air and for releasing can be purged of the compressed air, and on the other hand delimits a spring chamber, which receives spring means preloading the piston and/or the diaphragm into the release position of the service brake, wherein the pressure chamber comprises a pressure connection, which can be charged and purged by a brake line.
Such service brake devices mostly have an ABS control. The objective of an anti-lock braking system (ABS) is to regulate or limit a brake slip that occurs on wheels to an optimum slip. An optimum brake slip amounts to for example 12%. The brake slip is determined by comparing the wheel speed of the wheel concerned with a central reference speed. To this end, the ABS control, starting out from a level corresponding to the respective brake request, can lower the brake pressure in the brake cylinders (pressure lowering), hold the brake pressure in the brake cylinders (pressure holding) and increase the brake pressure in the brake cylinders to the starting level corresponding to the brake request (pressure increasing).
With a service brake device known for example from DE 10 2013 000 275 A1 active pneumatic service brake cylinders in diaphragm and/or piston design are present, which in turn are supplied with compressed air via ABS pressure control valves arranged in the brake lines. During all charging or purging operations, the compressed air has to be conducted via the ABS pressure control valves which, dependent on the pressure ratio, takes place relatively slowly. In electronically (brake pressure) regulated brake systems (EBS), the brake cylinders will be charged or purged by pressure regulation modules which also control the brake pressure in the brake lines as part of the brake slip control (ABS). In the generic DE 10 2013 000 275 A1, a quick air release valve is arranged between the service brake valve and the ABS pressure control valves of the front axle. This quick air release valve responds to a quick releasing of the brake pedal by the driver and then ensures a rapid purging of the brake lines.
In the event of a full brake application with ABS control, the pressure reduction gradient during the pressure lowering plays a major role for the regulating quality and thus also for the stopping distance. Desirable during the pressure lowering as part of an ABS control intervention is as high as possible a pressure reduction gradient with rapid depressurization of the brake cylinders.
Compared with this, the invention is based on the object of further developing a service brake device of the type mentioned at the outset in such a manner that as fast as possible a depressurization of the brake cylinders is possible. This rapid depressurization is to be possible in particular in the event of an ABS control intervention.